Conventionally, the absolute configuration of chiral compounds has been determined by circular dichroism (CD) spectrophotometric measurement of a complex of a chiral compound and a specific compound based on the correlation between the sign of the Cotton effect and the absolute configuration of chiral compounds. For example, the following methods are reported.
(1) X. Huang, B. H. Rickmann, B. Borhan, N. Berova, and K. Nakanishi (J. Am. Chem. Soc., 1998, 120, 6185-6186) report that circular dichroism is induced when chiral compounds are coordinated to a long chain-crosslinked porphyrin dimer, and there is a correlation between the sign of the Cotton effect and the absolute configuration of the chiral compounds.
In this system, however, circular dichroism is induced only when one chiral compound is simultaneously coordinated to two porphyrin units. Therefore, this method is useful only for bifunctional chiral compounds such as diamines, aminoalcohols, etc.
(2) M. Takeuchi, T. Imada, and S. Shinkai (Bull. Chem. Soc. Jpn., 1998, 71, 1117-1123) report that a porphyrin dimer having a phenylboronic acid unit exhibits circular dichroism in the presence of various sugars.
This system is applicable only to sugars which bind to boronic acid, and it is not a system for directly determining the absolute configuration of any specific-asymmetric center among the many asymmetric centers of sugars.
As is clear from the above, there have been no reports of a method for determining the absolute configuration applicable to a wide variety of chiral compounds, such as monoalcohols, etc.
X-ray diffraction is a known method for determining the absolute configuration of chiral compounds. However, the compounds to which this method is applicable are limited to crystalline compounds.
The present inventors have investigated methods for precisely and easily determining the absolute configuration of various chiral compounds. In recent years, they have found that circular dichroism is induced when a chiral compound is coordinated to a metalloporphyrin dimer containing Zn, Fe, Mn, or Ru as the central metals, and the sign of the Cotton effect and the absolute configuration of the chiral compound are correlated with each other. A novel method for determining the absolute configuration of chiral compounds was thus completed based on this finding (Japanese Unexamined Patent Publication No. 2001-220392).
However, even this method arises a problem such that the induced Cotton effect cannot be detected in the case of a chiral compound of a monoalcohol, etc. unless the sample solution is cooled to about −80° C.